1. Field of the Invention
The present invention relates to a lens barrel that changes a focal length, increases a barrel length under a shooting condition, and decreases the barrel length under a retracted condition, and to an image pickup apparatus equipped with the lens barrel.
2. Description of the Related Art
Conventionally, various techniques to shorten the barrel length under the retracted condition have been suggested with respect to a zoom lens barrel that increases the barrel length under the shooting condition and decreases the barrel length under the retracted condition to retract the lens barrel into a camera body (a retractable lens).
Japanese Laid-Open Patent Publication (Kokai) No. 2004-347615 (JP2004-347615A) discloses a lens barrel that can further decrease a length in an optical axis direction (the barrel length) as compared with an ordinary retractable lens barrel that can extend and can be retracted into a camera body, and a camera equipped with such a lens barrel. FIG. 17 is a sectional view showing a configuration of the conventional lens barrel described in the above-mentioned publication. This lens barrel 800 is capable of varying its barrel length between a retracted condition with a short barrel length and a shooting condition with a long barrel length. The lens barrel 800 reduces a length in an optical axis direction by opening an aperture of a lens shutter 900 and inserting a lens group 852 into the aperture under the retracted condition.
Moreover, Japanese Laid-Open Patent Publication (Kokai) No. H10-111444 (JP H10-111444A) discloses a zoom lens barrel with a shutter that is able to shorten a length in an optical axis direction under the retracted condition.
However, the above-mentioned conventional lens barrel has a problem that the barrel length under the retracted condition cannot be shortened enough.
Moreover, the lens barrel in the Japanese Laid-Open Patent Publication (Kokai) No. 2004-347615 (JP 2004-347615A) has a configuration where a light-amount control member such as a lens shutter is opened compulsorily more greatly than the maximum aperture at the time of shooting by a rodlike member, when the lens barrel shifts to the retracted condition from the shooting condition. Accordingly, unnecessary power is applied to the light-amount control member, which may break the light-amount control member.